2002 1500 5.9L - Overheating

I have a 2002 1500 5.9L that just recently started to overheat. I have replaced the thermostat and flushed the coolant. Last year the water pump was replaced.

When I start it up and let it Idle it can run for 2+ hours and not over heat but after about 10-15 min driving around the city or about 40 min on the highway it starts to climb above normal. In the first 5 min it will get up to normal then it appears the thermostat opens and the temp drops about a 1/8th inch on the gauge then slowly climes back to normal and keeps climbing. It never makes it to the red since I generally turn on the heater to bring it back to normal. I had the trans flushed and differentials.

I was going to check the fan clutch or sensor, but I need to do a little research on these two since I am not an expert on engines. Is there anything else that people have run into that I should be considering?

On an unrelated topic I have read some posts about oil sludge building up in the 2002 trucks and causing the engine to fail. Is that just with the 4.7L or do I also have to worry about that with my 5.9L?

Thanks
Drew

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ok, the 5.9 is pretty simple, cooling wise. from what im hearing here it sounds like you have a faulty thermostat. it could be possible you put the thermostat in the wrong way.... if your fan clutch was bad, the fan would be engaged all the time constantly pulling air. you may also want to check the waterpump pully for play as they tend to not last very long , especially if you got a cheapy valuecraft unit. a bad fan clutch can cause a waterpump to go south quickly
when you flushed the coolant, did you flush the heater core? could be some gunk in there causing problems, not common but ive seen it happen.
to check the fan clutch let the motor cool to ambiant temp. and see if you can spin the fan blade, if not your clutch is siezed.

a popular mod for alot of people on here is to switch out the clutch fan for an e-fan. fyi.

havnt heard any sludge issues with the 5.9, though the biggest problem with this motor is the plenum gasket. search the 2nd gen ram forum for that and a plethora of info can be found on that problem.

also, welcome to DF!

__________________
Listen.. I would never hit you with an axe.. when you had skewers stabbed through your mouth. I would figure one or the other would be enough..
5.9L truck club founder (retired)

Feel all over the radiator after the truck is hot. I could touch about 95% of my rad bare handed when my rad was clogged and only about 5% was screaming hot. Flushing radiators doesn't work in my experience so replace it if it's plugged.

i had the same problem in my old 1999 5.9L Durango, i replaced the thermostat, flushed the radiator and nothing worked...then i realized that my water pump needed to be replaced. fixed it instantly and never had that problem again...then i sold it and got my Ram so idk how it is now but i had it about 4 months after replacement and selling it so that may work for you.

I have a 2002 1500 5.9L that just recently started to overheat. I have replaced the thermostat and flushed the coolant. Last year the water pump was replaced.

ok, with that said, 1st question, did you replace the thermostat and flush the coolant after it started to overheat or did you do a regular maintenance with new coolant and thermostat, then it just started to overheat?

I had replaced the thermostat and flushed the coolant after I was having the overheat problem not as general maintenance.

I ended up replacing the fan clutch (I had ordered it prior to the first response). For the last couple weeks I thought that solved the problem, while I drive around the city it stays right at normal temp. This past weekend I went out of town and noticed that after driving on the highway for 15-20 min when I would slow down to a stop light it would start to to heat up when I would take off it would drop back to normal. After about an hour on the road it would run just above normal. It would never run hotter than halfway between normal and the top end of the gauge (approx 1 cm right of normal).

On the way home I ended up towing a buddies boat, had the AC running, and it was 85 degrees. It started out normal, dropped a half a cm, then slowly climbed to about 1 cm past normal and stopped climbing.

I checked the thermostat, it is not upside down and I have it in the 12 o'clock position. I bled the air out of the system. I have not felt the radiator to see if that is plugged, that is a good idea. If all of the radiator feels hot then it must be the water pump? I was hoping that it wasn't since it was just changed out last year.

I felt both the upper and lower radiator hoses and they are both hot to the touch so I assume the thermostat is functioning properly. I felt the radiator and it was too hot to touch on the top and I could hold my hand on the bottom without removing it. I am going to swap out the radiator tomorrow.

I noticed the transmission cooler is pretty dinged up with little stones (MN winters) and bugs, I was wondering if I should also replace this due since it may be restricting some airflow. What do you think?

Just wanted to update the situation. I replaced the radiator and gave the heater core a good flush. The problem is solved, it hit 97 degrees with high humidity and it did not overheat at all. I drove stop and go in the city, was on the interstate, and sat in some rush hour traffic with the AC on.

In normal driving, my temp gauge points in the middle. When driving in very hot weather in heavy traffic with lots of idling, the gauge climbs into the red. Is this normal or is there some issue with the cooling system that needs maintenance? The fan clutch works as I can spin the fan by hand when the engine is shut down. Any ideas?

In normal driving, my temp gauge points in the middle. When driving in very hot weather in heavy traffic with lots of idling, the gauge climbs into the red. Is this normal or is there some issue with the cooling system that needs maintenance? The fan clutch works as I can spin the fan by hand when the engine is shut down. Any ideas?

no it is never normal for the temp gauge to climb into the red.. post a new thread about your problem as this thread is over a year old.

and that might just be your problem, the clutch fan might be bad. if you can spin it with your hand that just means its not locked up.. my guess would be that the fan isnt engaging when the motor heats up.

__________________
Listen.. I would never hit you with an axe.. when you had skewers stabbed through your mouth. I would figure one or the other would be enough..
5.9L truck club founder (retired)

Work on the cheaper stuff first. Fan clutches are not expensive and relatively easy to replace. When the motor (and the air) is hot, can you turn the fan? If so, it's likely not engaging properly. If it runs hot in traffic, but not on the highway, the radiator is probably still OK.